The subject matter of the present application is related to U.S. Ser. No. 406,551, filed Sept. 13, 1989entitled "Printed Circuit Board Having An Injection Molded Substrate" naming Marcel Heermann as the inventor, and assigned to the same assignee as the present application.
The present invention relates to a printed circuit board having an injection molded substrate, with a surface comprised of trench-shaped depressions in the region of interconnect and traces of planar depressions in the region of through-connections and/or the region of connecting pads The recessed regions contain a conductive metal coat.
As will be understood by those skilled in the art, the term interconnect pattern refers to all of the electrically conductive structures which are utilized on a PC board. The term "interconnect trace" refers to the conductive path which extends between any two connection points on the board. The term "throughconnections", as used herein, refers to two types of printed circuit board structures. The first structure relates to the metalized holes which connect the conductor paths of one wiring level of the PC board to another wiring level. The second structure referred to as a "through connection" is the metalized hole which is used to accept a component, such as a resistor lead or an integrated circuit pin, therein. Finally, the term "connecting pad" refers to the planar areas of the circuit pattern which serve, for example, for the connection of components or connecting wires.
These terms have been defined for clarification purposes only. However, the definitions set forth are not meant to be all inclusive. Accordingly, the terms should be accorded their full scope as they would be understood by those skilled in the art.
Printed circuit boards having an injection molded substrate or a similarly formed substrate are disclosed in DE-A-27 15 875 and the corresponding CA-A-107 58 25, and in U.S. Pat. No. 4,532,152.
In order to manufacture the printed circuit board disclosed, for example, in DE-A-27 15 875, the substrate is first developed into a form in which the conductive pattern and the through-connection holes are contained in the shape of depressions. After mechanical and/or chemical surface treatment, the substrate is then chemically activated. Once this has occurred, the raised surfaces of the substrate are covered by a protective layer. Only the depressions have to remain free during the application of this protective layer. Therefore, it is no longer necessary to have an involved photostructuring of the resist but rather the application can be done, for example, with a doctor or by roller coating. Next, the conductive metal coat is applied. The coat is preferably applied by currentless metal deposition. The metal coat leads to the formation of the entire conductor configuration in the depressions of the substrate and in the through-connections holes. Finally, a solder stop lacquer is applied on the conductor surfaces which are not numbered in any solder connections.
By structuring the substrate before the selective metallization, the corresponding resist does not need photostructuring. However, the application of the solder stop lacquer require either a selective application onto the interconnect traces or photostructuring. One of these two methods are required in conventional circuit boards and manufacturing methods, since the planar depressions, which surround the through-connections as solder eyes or which serve as connecting pads, must remain free of these solder stop lacquer.